1. Field of the Invention
This invention relates in general to semiconductor devices and in particular to the electrical coupling of structures of two wafers.
2. Description of the Related Art
Some semiconductor devices such as a MEMS semiconductor devices utilize cap wafers for providing a protective cavity for the MEMS device during operation. A MEMS device is a micro-electrical mechanical device that is typically manufactured, in some embodiments, with semiconductor device processes. Examples of MEMS devices include accelerometers, sensors, micro motors, and switches. In some examples, MEMS devices include parts (e.g. proof masses) that move during operation. Because of this movement, a cavity is used to protect the part while allowing for movement of the part.
A cavity can be implemented by forming an opening in a cap wafer and bonding the cap wafer to the device wafer where the opening overlies the MEMS device. Afterwards, the cap wafer and device wafer are singulated to form the MEMS die.
One problem with implementing a cap wafer in some examples is that a good grounding coupling with the device wafer is needed. In some examples, the grounding coupling is made with wire bonds from the cap wafer to the device wafer, conductive vias through the cap wafer to the device wafer, or conductive bonding material between the cap wafer and the device wafer.